Warfarin (Coumadin) inhibits clotting factors II (prothrombin), VII, IX, X. This is accomplished by suppressing vitamin K in the clotting cascade. Vitamin K is used in the clotting cascade to activate certain clotting factors.
Atrial fibrillation results when there is ineffective atrial contractions. This leads to blood stasis in the atria, which can result in thrombus formation, increasing the risk of stroke and other embolic events. Warfarin prevents clot formation.
Thrombosis is a blood clot that forms in the blood vessel that can partially or fully obstruct the blood flow. Thrombosis typically happens in a deep vein, which is known as a Deep Vein Thrombosis (DVT). These clots can break off and travel to vital organs resulting in restricted blood flow. Warfarin prevents further development of the thrombosis.
Pulmonary embolism is a life-threatening event where a thrombus becomes lodged in a pulmonary artery blocking the circulation. An emboli typically evolves from a thrombosis. Patients with high risk or past events of a PE are often placed on Warfarin.
Prothrombin time (PT) and international normalized ratio (INR) levels will be routinely checked on patients taking Warfarin. Educate the patient on the importance of these routine appointments as their dosage will change depending on their blood levels. Therapeutic levels for the INR depend on the provider and diagnosis, but can range between 2.5-3.5. These values are frequently followed at the beginning of treatment and are tapered off to every 2-4 weeks once stable.
Bleeding gums while brushing teeth or prolong bleeding when a laceration is present can indicate that the INR is elevated. Gastrointestinal bleeding may occur with patients that are taking Warfarin. Educating the patient to monitor stool color can help inform the patient when to seek medical attention.
Warfarin is contraindicated in pregnancy as it is a teratogen, an agent that causes birth defects. Patients should be educated about the importance of notifying their physician if they are pregnant or trying to become pregnant, so that an alternative medication can be prescribed, such as heparin instead of warfarin. Warfarin crosses the placenta as well as enters breast milk.
Vitamin K (phytonadione) is the antidote for warfarin. A typical dose is 10mg in 50cc IV bag that boluses over 15 minutes. Fresh Frozen Plasma (FFP) can also be given depending on the INR level.
Warfarin has a prolonged time to reach therapeutic levels which usually takes 2-3 days. Remember that patients are still at risk for thrombotic events during this time and are usually administered heparin alongside warfarin until therapeutic levels are reached.
Educate the patient to maintain a consistent diet and to notify their provider of any dietary changes. Changes in consumption of foods high in vitamin K like green leafy vegetables may alter plasma levels of vitamin K.
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